The present invention relates to a thermal analyzer for measuring a signal indicating variations in the physical or chemical nature of a sample as a function of temperature or time. More particularly, the invention relates to a novel thermal analyzer which permits the interchange of thermal analysis data arising from different heating rates of a sample and which, at the same time, allows a thermal analysis of the sample to be performed in a greatly shortened time.
Thermal analysis is a powerful means for investigating how a physical property of a material or sample varies with temperature.
Typical thermal analyzers include the differential scanning calorimeter (DSC), differential calorimeter (DTA), thermogravimetry instrument (TG), and thermomechanical analyzer (TMA). These instruments measure enthalpic balance of samples, differential temperatures (qualitative enthalpic balance), weights, and the dependence of various lengths on temperature (variations in physical or chemical properties of samples), respectively.
In thermal analysis, a physical property of a sample and temperature variations are continuously measured while heating the sample at a given rate. At this time, the dependence of the physical property of the sample on temperature can be derived from the relation between the temperature signal and the physical property signal. Various thermal analyzers for performing analysis of this kind are commercially available and used industrially for research and quality control purposes.
In the prior art thermal analysis described above, it is customary to heat a sample at a rate of 5 to 20 degrees/min. For example, if a temperature range of about 1000 degrees is scanned, it takes 1 to 3 hours to complete the scan. In view of this, the prior art analysis has disadvantage in that the time efficiency is low.
An ordinary thermal analyzer can perform a measurement operation at a heating rate of 50 to 100 degrees/sin. This shortens the measuring time. In spite of this, relatively low heating rates of 5 to 20 degrees/min are often used for the following primary reason. If a sample inducing plural reactions during scanning of the temperature is heated at a high rate, these reactions tend to overlap. The resulting data is inevitably cumbersome to analyze.
Thermal analysis is intended to investigate the dependence of a physical property of a sample on temperature. Detailed investigation of the measured signal indicating the physical property has shown that the physical property signal is observed to depend on time as well as on temperature in practice. The two main reasons for this are:
1) A detector for detecting variations in the physical property of the sample has intrinsic time constant.
2) The function of temperature is not the total amount of reactions induced in the sample but the reaction rate (i.e., the reaction ratio per unit time).
After thermal analysis of a sample is conducted at a varying heating rate, it measured data are simply taken as physical property values that are functions of temperature, and if they are compared, then results of the measurement are that the same sample shows different decomposition and reaction temperatures reflecting the time dependence effects of the physical property.